Method of making resilient smoothsurfaced floor covering materials



Nov. 22, 1960 R. J. RAINAR 2,961,029

METHOD OF MAKING RESILIENT SMOOTH-SURFACED FLOOR COVERING MATERIALS Filed June 7, 1956 DECORATIVE WEAR- RESISTANT LAYER BEATER SATURATED FELT HAVING A BUTADIENE- STYRENE COPOLYMER BINDER FOAMED AND VULCANIZED RUBBER LATEX INVENTOR ROBERT J. RANYAR ATTORNEY United States Patent METHOD OF MAKING RE'SILIENT SMOOTH- I SURFACED FLOOR COVERING MATERIALS Robert J. Rainar, Manor Township, Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Filed June 7, 1956, Ser. No. 589,858

Claims. (Cl. 154-25) This invention relates generally to resilient smooth-surfaced floor covering materials, and more particularly to such floor covering materials having a foam backing. Still more particularly, it relates to a foam-backed floor surfacing material which possesses to a high degree the requisite characteristics of a sturdy, long-lived, comfortable flooring material. The invention also relates to a method of making such floor surfacing materials.

In the past, one or more layers of a rubber foam or cellular structure have been placed on various other materials in order to impart a soft, resilient structure to the finished article. Such articles have been useful as upholstery, shoe products, crash pads, table coverings, and articles of wearing apparel such as brassieres. There has not been developed, however, any practical method for making a resilient smooth-surfaced flooring material which incorporates a foam rubber backing as an integral part of the flooring. There has been good reason for this situation.

Flooring materials must posses'certain characteristics to. be useful. They must be strong, wear-resistant, waterand alkali-resistant. Additionally, they must feel.comfortable under foot; they must not emit a hollow sound when the foot strikes the wearing surface. They must possess unusual indentation properties in order that heavy furniture and heavy trafiic will not permanently deform the flooring. They must be so manufactured that they can be permanently adhered to a subfioor by means of adhesives and must lend themselves to installations of intricate shape and varied pattern. Additionally, most flooring materials must be fabricated on equipment which utilizes heat and pressure and which forms a hard, nonporous. article in order to meet the above-described requirements. .This type of manufacturing process is exactly the opposite of the type of procedure necessary to form an article to Which a rubber foam will adhere.

Although foam rubber articles in the form of sheets and pads have been used as underlayments for soft-surfaced rugs and carpets, such underlayments cannot be used for the resilient smooth surface floorings in view of the peculiar requirements of such floorings. Thus, not

only has there not been described in the past a unitary article. of a wearing surface and a foam backing as a flooring, but it has not been possible to achieve a combination of smooth surface resilient flooring on a supporting layer and a foamed rubber underlayment by any practical means.

2 It is the primary object of the present invention to present a resilient smooth-surfaced flooring having as an in.-

tegral part thereof a foamed rubber backing; no adhesives of any kind are present in they flooring. It is a further object to present such a flooring material which possesses the requisite stringent characteristics which necessarily define a suitable floor covering. A further object is to present a method of. making such a fioor covering. Other objects and advantages will be apparsnti' h discussion el w- "The invention contemplates a resilient smooth surface "ice floor covering comprising in combination a water-repellent beater saturated felt containing butadiene-styrene copolymer deposited on the felt fibers as a binder for the fibers. Adhered to one surface of the felt without adhesives is a decorative wear-resistant layer, preferably of linoleum composition or of a vinyl chloride resinplasticizer-filler composition. Adhered to the other sur-- face of the felt without adhesives is a layer of foamed and vulcanized latex containing at least about 50% by weight mineral filler based on the weight of rubber solids in the foam.

The attached drawing illustrates the laminate structure of the floor covering prepared by the process of the present invention.

One of the surprising features of the present invention is that the backing material for both the wearing surface and the foamed rubber layer must meet certain narrow and rigid requirements. Backings for foamed rubber used in the past for other products have all achieved good keythat is, good adhesion between the foamed rubber and the backing, by mechanical means. The foam has physically penetrated the fabric backing and on vulcanization has become firmly and mechanically fixed. This type of mechanical key is not possible with a floor covering, since the backing must possess characteristics of strength, flexibility, and others not met in any but the flooring art. The backing in the flooring art is of such nature that a permanent chemical and/ or mechanical key between the backing and the foam has been difficult, if not impossible, to obtain. Yet a strong, firm .key between the backing and the foam is essentialif the flooring is to remain in place in use once it has been permanently installed on the sub-floor by the use of adhesives. It has now been found that a strong permanent chemical and/or mechanical key can be obtained so long as certain conditions are met.

The backing for flooring materials must be prepared in a certain way With certain ingredients if the backing is to serve as a support, both for a suitable decorative wearing surface and a suitable foam backing. In the first place, the supporting layer must be a felted product as opposed to a fabric. Secondly, the fibers in the felt must be coated with a butadiene-styrene copolymer in order that a proper chemical key can be achieved between the felted supporting layer and the foamed rubber backing. 'A felt having thes'e'characteristics' must be prepared by the beater saturation process if it is to possess the requisite strength for use in flooring materials. The term beater saturated felt as used herein defines a felt prepared by well-known beater saturation technics.

The fibers from which the felt is made may be of various kinds. Rag furnish is preferred, but there may also be used asbestos, cotton linters, and other long fibers commonly used in the manufacture of felt as a supportinglayer in flooring material's.

The material to be deposited on the fibers in a chest iscritical. The binder must be a butadiene-styrene copolymer containing between about 20% and 55% styrene, usually between 45% and 50% styrene, and preferably about 50% styrene. It is completely unexpected to find that the butadiene-styrene copolymers are the only operable binders in the present invention. Neoprene v(polychloroprene) does not possess the proper aging characteristics for a flooring felt binder and does not allow a good permanent chemical key between the felt and the foam rubber. Additionally, the acidic nature of neoprene has an adverse effect on the felt. Butadienacrylonitrile copolymers do not allow the formation of a suitable key between the felt and the foam in flooring applications. Natural rubber does not. form suitable sheets for flooring, applicationsby the beater saturation t'echnics. Asphalt saturated sheets act like neoprene sat;

poor permanent keys between ing' felts to. achieve the (necessary waterrepellencynand other physical characteristics, only the'butadicne-styrene cop'olymersare suitable. This is completely unexpected. It is essential thatthje butadiene styrene copolymers be placed ontheffibers b'y' thejbeater' saturationtechnic and not by one of the "manyafter-impregnationtechnicm If an attempt is. made .to. impregnate .a felt .with but'adi'enestyrene cop'olym'ers afterthe felt hasbeenformed, in-

' complete "impregnation takes place; "This will. be true unless the felt is loosely made. to allow adequate penetration of-the butadienerstyrene copolymer. But in such' case the .felt is'th'en 'insufiiciently strong to serve as a supportfor the decorative wearing surface for-(flooring materials. This is also true of felts 'after impregnated with natural rubber. I

' The amount'of'butadiene-styrene copolymer tobe deposited on the fibers may vary within certain limits. Amounts less. than about 10%, by weight copolymer based on the dry weight of the fibersdo not yield a suificiently strong sheet for flooring purposes, and additionally fbegin todiminish the. strengthof the chemical keytbetween the beater saturated felt and the foam backing. n the other hand, more than about 80%by weight butadiene-styrene copolymer' basedon thedry weight of r the. fibers produces a rubbery sheetfwhichm'ay 'bejoo flexible and which haspo'oncutt'ing characteristicsxwhen serving as'a supporting layerforza .decorativef'wearin'g surface in flooring materials. 'Aboutfll15 %l3 0%fby Although the wearing surface may be any of those vthe flooring art, such asprintedfilm's, rubber compositions, and other surfacing materials it is preferred that the wearing surface 'be a linoleum composition or a'vin'yl chloride resin-plasticizerfiller composition.

carbonate, and other conventional fillers and'other addi: tives. Linoleum cements typically are made from a drying oil and a resin, usually rosin, bya..number of methods which result 'in the production of a siccative oil-resin gel by oxidizing and polymerizing .thedrying about 50% to about 70% by weight of the wearing surface composition. Thefillermayinclude a preponderhnt 3 portion by volume of fibrous filler such as wood flour, cork particles, asbestos and other mineral fibers, and the 1 a 1 like. The remainder or the total-of the filler component 3 is comprised generally of finely divided particles such as whiting (calcium carbonate), clay, silica, slate flour, and 7 similar nonfibrous filler material; The final mixture may" alsdincludeysmalhbut efiectiveyamounts'gf' welieknownvulcanizing agents, curing accelerators, lubricants, pig-I rner 1ts,'and the like, par.ticula rly 1 where a curable synemulsion"stabilizers,thickening-agents,accelerators}gell thetic rubber is 'admixedlwithpthe vinyllchloride resin.

The total, amount of' such compounding agents, whenused at all,'is-.generally"up Ttofiabout. 10%. by weight of the filler. In additio n. to the plasticizers such as dioc tyl' phthalate, butyl octyl phthalate, and tricresyl'phosphate, other, well-known plasticizers such as epoxidized drying oil acids may be used.

The syntheticrubber latex fromwhich the foam back ingis prepared maybe madeby. emulsion polymerize; tion by methods well-known in the priorgart. The late;

to be formed isone of highirubber content, for example V 50% to 72%,:and may be prepared in low or high solids concentration directly" by emulsion polymerization or by centrifugin c'reaming; or otherwise concentrating low solids latices; .Conventionalmodifying: agents such as vulcanizing agents Q (preferably sulfur), antioxidants,"

ling "agents, fillers; coloringagents; and other modifying materials areaddedto the-,latenprior to or duringtlie foam f'ormation operation.- :TheLemulsifying agents used in the practice of invention 31 5 and other organic chemical? t compounds which have "both hydrophilic, and hydro? decorative wearing surfaces customarily employed in 5 i Oil, generally in the presence of the resinous material. 7

Such cements are generally made'with linseed .oil, al-

though in recent years the linseed oil has beenreplaced .wholly or in 'part by tall oil, tall oil fatty acids, or tall 1 oil esters. Thelinoleum compositions may contain small amounts of a compatible syn-theticrubber; Inany case,

' the' linoleum compositions are calendered onto sheets and the resulting product cured and otherwise treated to produce the. well-known linoleum so useful .as a flooring material. 1

In recent years, a resilient smooth surface floor covering has been produced by forming a composition con- The composition is calendered' into a sheet or it may be molded or otherwise formed, and then it by weight of the vinyl chloride resin and about 30% to j-about 10% by weight of the plasticizer or plasticizer j mixture. Compatible synthetic rubbersi may 'begpresen't. when admires-1 with filler; th gfillefr' en rally compri e Sodium fiuorosilicate'tNA siF is the gellingagent of 'ftaining fillerand a binder that includes a vinyl chloride -resin and a plasticizer for the resin, preferably. ofjthe ester type.

phobieradicals so as to; promote; the mixing of oiland water-miscible ingredients "in the latexand stabilize emulsions. so. formed. A wide variety of ,theseqcom pounds iskn'own and availablefcommercially. For example, potassium 'oleate "soap, rosin'ateEsoaps,fsoditint stearate; po't assium lauryl sulfate,sulfonatedjhydrocar 5 bons, and sodium ,alkyl naphthalent. sulfate are examples;

of typical wetting agents useful in stabilizing the lateii In thepracticegof the present invention; it

emulsions. V has "been found .that a soap formed from a 'mixture'of higher fatty acids containing -linoleic, l inolenic, andgoleieq .acids yields a more desirable soap on treatingthe acids" with the amount of potassium hydroxide solution needed, 'for neutralization, Forthe. purposes of av flooringbaclg I a .ing," a foam prepared with a rr;ixture of these soaps is superior to'afoam prepared" with, the earlier described; moreconventional soaps. These latter emulsifying agents serve an additional role of -foa ming agents andflfurthefr aid in maintaining the froth or foam in a stableform until the curing operation :is completed. 7 V

V The foamablelatexcomposition must containa gelling agent to induce theformation of' a stable solid foam);

choice, although ammonium sulfate, ammonium nitrate,

and 2-nitro-2 -methyl-l-propanolfmaybe used. Although it occasionally may be desirable to use two or more gelling agents, for -.example sodium fiuorosilicate ammonium sulfatersuch is not necessary. 1

Sensitizers, antioxidants, and ultra accelerators should be used as is conventional in the rubber A common sensitizing agent for foam useful in theflooriug is triethyl trimethylene triamine sensitizer sold under lthe.

name .Trime'ni: Base." The antioxidant may be phenylbeta-naphthalamine, amine, and l the heptyl diphenylamines' sit-9), zinc dimethyldithiocarbamate, zinc diethyldithiocarbarnate, zinc. dibutyldithiocarbamate, or others which provide maximum curing activity.

Modifying'agentssuch as caster .oil may'beaddedlto .improve the slash? grannies of 1th? fQf m i ihQl l fwi h r L di-bta-naphthol-Iama-phenylenedif Suitable ultra accelerators are-activated dithiocarbamate {Setsit-SiSeta foam to be used for-flooring materials, care must be taken not to render the foam too elastic. In view of the use as a flooring, the cell tack in the foam must be reduced, and this can be accomplished best by the addition of a emulsion such as an emulsion of paraflin wax in water. Fillers such as carbon black, magnesium oxide, zinc oxide, and preferably calcium carbonate, should be added to stiffen the foam. Carbon black may serve this role and in addition will serve to impart color to the final product. Dyes or pigments may be added to controlthe color as desired.

, It is in the filler content that the foam suitable for use in the combination of the present invention departs most widely from prior foams. Prior foams seldom, if ever, exceed a filler content of about 35% by weight based on the weight of the rubber solids. Such a low loading has been found unsuitable for use in a flooring material. The foam must contain at least about 50% by weight mineral inorganic filler based on the weight of the rubber solids in the foam and preferably about 75% by weight in order that the foam will exhibit suitable compression characteristics to be useful in combination with the decorativewear surface and the felt supporting layer described earlier. The preferred filler is a finely ground mineral inorganic filler customarily employed in the rubber art, or equivalent fillers giving suitable compression charac carbonate, clays, silica, slate flour, and the like; calcium carbonate filler is the filler of choice.

The latex to be used in preparing the foam useful in the present invention should be either a natural hevea latex or one which has been replaced to the extent of up to about 50% by weight with a butadiene-styrene copolymer latex; preferably the latex will be a 70:30 rubber latex mixture of heveazbutadiene-styrene copolymer. The latex should be blended with the sensitizer and the soap, and the vulcanizing dispersion, in part or all, added along with the wax emulsion, and the mixture allowed to mature. The rate of maturation depends both on time and temperature, the higher the temperature, the shorter the time. A good time temperature relationship has been found to be 16 hours at about 85 F. During maturation, the mix must be maintained under proper agitation such that no settling out ofany of the ingredients occurs but such that no air is beaten into the mix.

The matured batch is then mixedwith further small amounts of the triethyl trimethylene triamine sensitizer and the potassium fatty acid soap. The ultra accelerator, the pigments, and the inorganic mineral filler, or equiva-- lent, are also added and thoroughly intermixed with the other ingredients. Thefiller is preferably added in the form of a slurry.

The compounded and matured latex is then vigorously agitated or whipped with air, nitrogen, or the like to produce a froth or a foam. Suitable apparatus to accomplish the foaming is the Oakes foamer or blender, a Hobart foamer, a Marco foamer, or any device which will incorporate a gas into the mixture to form a foam. To prevent premature coagulation, it is preferred that the zinc oxide in the form of a slurry be added at the foaming head. The sodium fluorosilicate or equivalent gelling agent may also be added at the foaming head, but it is preferred to add the fluorosilicate during an additional blending operation subsequent to the actual frothing or foaming operation. Thus, a preferred embodiment of the process contemplates adding the zinc oxide slurry atthe foaming head during froth or foam formation, passing the foam to a secondary blender, adding the sodium fluorosilicate at this point, and then distributing the final mixture to the point where it is to be applied to the felt supporting layer. The temperature during the foaming steps is preferably maintained within the range of about 50-75 F., and more preferably between about 55-60 F.

The foam is delivered to the pointwhi used by means of flexible hoses. Since a continuous process is the only practical type of process for flooring applications, the foam is delivered to a point where it may be placed upon the felt-wearing surface combination described earlier. The combination may be unrolled and passed down a table underneath a doctor blade, or roll or similar device, felt side up. The foam is deposited along the width of the moving felt to form a puddle or bank of foam behind the doctor mechanism. The doctor mechanism should preferably be chilled to retard premature coagulation of the foam. The thickness of the foam deposited is easily adjusted by maintaining the proper spacing between the doctor mechanism and the' felt. For flooring material application, the foam thickness will vary between about and M4". The stiff-- ness and flexibility characteristics of the decorative wear-- ing surface determine to a significant extent the thick-z, ness of the foam on the other side of the felt. Stifier: wearing surfaces call for thicker foam backing.

Once the foam has been deposited on the felt support-- ing layer, sufiicient time must be allowed for the foam to: gel. The time is largely controlled by the amount of gelling agent added, which should be such that gelation; occurs within about 2 to 5 minutes from the time thefoam has passed beneath the doctor mechanism. If the gel time of the foam is too short, thefoam may gel in'. the bank behind the doctor mechanism. If the gel time;

is too long, the felt supporting layer may absorb sufiicient water to destroy the structure of the foam. Geli time is also related to some extent to the water absorp tivity of the felt. It is for this reason that the felt must, have some degree of water-repellency. Otherwise the foam structure would be destroyed as soon'as the un-v gelled foam contacted the felt.

Subsequent to gelation, the foam is cured or vulcanized,

by heating to an elevated temperature, preferably in the range of about 210 F. until the foam is dry and cured. A preferred embodiment of the present inven tion entails heating and curing the foam under radiant heaters. Alternatively, the flooring may be suspended in suitable stoves or ovens which are then raised to the. requisite temperature and maintained at that temperature until drying and curing are completed.

The following examples illustrate specific embodiments of the present invention:

Example I A felt supporting layer measuring 0.043" in thicknesswas made by the beater saturated technic from a. rag furn sh on which had been deposited 20% by weight, butadiene-styrenecopolymer (50% styrene) based on the.

dry weight of the fibers.

The following mixture was formed into a sheet, cooled,.

and broken up into chips.

Pounds 5 0250 mixture of vinyl chloride-vinyl acetate copolymer containing 5% vinyl acetate, and vinyl chloride-vinyl acetate copolymer containing 13% The chips were deposited on the felt supporting layer and subjected to heat and pressure in molding presses to consolidate the mixture on the felt. 1; After cooling, the above material, feltv side 111 5..

passed down a table, at one end of which was tuo tiftttui 1 a doctor. mu in the-form of a chilled cylinder. Foam Was.;dlivered;along the width of the-felt supporting layer beh d-1 .thedo o m Thefoamwajs madees follows; c p

,A latex dispersion wasmade'containingthefollowing .A: vulcaniz ingdis'prsion containing-the following ingradients was. well dispersed inwater to. achieve 50%- solids and was added.v to the above latex composition.

Ingredients Pound Sulfur '2 Zinc diethyl dithiocarbamate (ethyl Zimate) 1 Sym. di-beta-naphthyl-pphenylene diamine (agerite white) 1 Zinc salt of mercaptobenzothiazole (Zetax) 1 'Three pounds of a wax emulsion of para'fi ina'nd water containing about 50% solids was added to'the above two mixtures. The entire mixture was then maintained at 16 hours at a'temperature of 85 Fl while maintaining the mixture under agitati'onto prevent incorporation or air but to maintain the :solids in suspension.

To 172.5 pounds 'ofthe matured batch: there was added l'poundof the sensitizer and pound of the soap 0.5 pound of an ultra accelerator, namely'activated' dithioin water of finely divided 'calcium carbonate (Calwhite' T).' When the composition was" thoroughly mixed; it

Wasdelivered to an Oakes foamer, where the above amount was blended continuously and proportionately with 10 pounds of a 5 0% water slurry of zinc oxidelin the presence of nitrogen gas" under pressure. The foam from' th e Oakes' foamer head was passed to an Oalces" blender; where it was" proportionately admixed with 2% I pounds (dry basis) sodium: fluorosilicatej slurry containing 20% solids. From the Oakes blender,- the foam was delivered by means ofi'ilexible hoses to the point behind the. doctor roll asdescri bed above.

The doctor wasrset to. deliver a finishedfoam thickness off 0.04 "+0I050" (aftercure). The rate'of. feed of the fltf'supporting}layeri was'1'2 'feet per minute. Therate;

of the foam fed'wa's adjusted to. maintain a' minimum bank behind the doctor roll. 7 c g After passing under the doctor'roll, the felt carrying the foam traveled down a table where inspection showed that itIg'elled in 4 --minutes. v The foam was then passed under radian-t heaters: maintained at a temperatureof 480-520 F} Good cure resulted." t j The curedfo'am backing exhibited unusually strong adherence-to the felt supportingrlayer; This :is to be contrasted with the key existing between a foam-backed f product prepared Zas described 7 above save that the felt binder is a 'bntadienewacrylonitrile-copolymer; In'this even by hand.

lattercase, the foam was readily peeled from the backing :The producfmadeias described-in thisqexamplei pos-j sessed:all thelrequisitesof aheavy-duty flooring material;

Test installation brought to light the surprising {fact that the-Mmarks left by heavy .fnrniture-standing for extended periods" on the flooring materiadlwere not as noticeable in the case of the foamb acked 'matei ial' as they were in the -case of similar materialsfprepared on'imor conven tional felts without a' f danrf'b afckin'g'; residual indentation V ot -iroa nbacktti'materiaii*wa superior. wither 51mm foam-backed material; Additionally; the standing dueto traificiand'other causes offtheioam-backed 'mater-ial was.

appreciably less than that'noted, in the conventional floor irigmatenials. Th'e foam-backed material .was jquieteru 1 and more comfortable under foot andididqafzhetter job el-iniinating-show through of floor irregularities" n -m 1s 11' "A felt w'as' preparedias'in Example r. '1 l from 73 parts byw Linoleiin'i c'mposition i as prepared weight wood flour, 117 parts byweight fWhiting (cal I m m-carbona e and 112 parts byi weight of a standard linoleum 'cement made of an oxidized mixture containing f,

56% of thejpar't-ial esters of tall oil and'pentaerythritoli and 44% linseed oil. The-composit ion'was sheeted out" to-formblankets, and the blanlgets were adhered to thefelt M byhot calendering in accordancewith known methods; After curing at- F. for l2'da'ys the deliveredto the table for theapplication of foam. 7

A foam simil ar to that applied in'Example I'was used, save that the starting rubber latex consisted of l 60 pounds 7 of natural latex; no butadiene styrene" copolymer latex wasflusedi I 7 V V V, H k After application and cure-iof-the foam in accordance withlExlar'nple I, a flooring material resulted which; on test installatiomproved itself to be comfo rtable' under foot strong, wearand stain-resistant, and superior to' the flooring without the foam backing. f

I" claim:

productwasi l. The method of r'nakiri g a resilient siric aoth :s urfacred.

forma foamed latex layer of eventhickness in, the rangei l of to A, gelling said foamedlatex layer; and heat t treating said foamed latex-layer to 'eause drying and" 'vnlcaniizationthereof. c

2. The method c ordingto claim whereiiiisai orative wear-resistant layer; comprise ino eum-compost: tion.

decorative wear-resistant 'la'ye resin-plasticizer fillr' co'rnpo c u 4. The method according {to cl foamed latex contains abo1it'75% by weig based 'on' the weight of ru bbei'c'solids'in sad 5. The method according to claim l who 5 saturated sheet contains about} 10% 8Q tadienestyr'en'e oopolyn'ier depos d .onth

7 1-1 6-T d..' td ns;to ela-i iiyvherein sa dtQ t; I V

contains about 20%-by;weight butadiene-styrene cppoly-j floor coveringcomprising f forming a t'walt'ererepellent'g beater saturated sheet-"coiitainirig but'adien'e polymer deposited onih'e fiber asa binder positing on one surface "of sai layer-selected froni 'the group positiojrrand'vinylfchlori sition'i subjecting saidj la yer ing to theother surfacefofs I latex ofat least 50%byeight natural lat x taining a vulcanizing"agent, gellingfageii landfabout 3. The nie'tlfod according'to 1i a inylchloride f 7. The-method of 'akinga;resilientfsmoothsurfaced" rubber solids in said.latex;"leveling ofiisaid mass to form:

a. res-med latex layer of even in tl'ie'range 10f 1 gg" fro /lz", gelling said foamed latex layer 'zandhea t 9 treating said foamed latex layer to cause drying and vulcanization thereof.

8. The method according to claim 7 wherein said foamed latex comprises a mixture of about 50% by weight natural rubber latex and about 50% by weight butacliene-styrene copolymer latex based on the weight of the rubber solids.

9. The method according to claim 7 wherein said foamed latex comprises a mixture of about 70% by weight natural rubber latex and about 30% by weight butadiene-styrene copolymer latex based on the weight of rubber solids.

10. The method according to claim 7 wherein said mineral filler comprises calcium carbonate.

References Cited in the file of this patent UNITED STATES PATENTS Van Horn June 6, 1933 Pennel et a1. June 20, 1939 Trepp Jan. 11, 1949 Scholl Jan. 27, 1953 Thompson et al. Feb. 24, 1953 Baymiller Oct. 11, 1955 Kolb Aug. 21, 1956 Baymiller Aug. 13, 1957 Banks Dec. 17, 1957 FOREIGN PATENTS Germany July 16, 1953 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 2,961,029 November 22, 1960 Robert J Rainar It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1' line 34 for "posses" read possess column 4 line 41 for "naphthalent" read naphthalene line 53-, strike out "a"; column 7 lines 7 to 15, in the table, first column thereof last line, for "2O/ read 20% column 8, line 1 for "standing" read staining Signed and sealed-this 2nd day of May 1961,

(SEAL) Attest- ERNEST W SWIDER DAVID. L LADD Attesting Officer Commissioner of Patent.

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION i November 22, 1960 Patent Nos 2,961,029

Robert J, Rainar It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 34, for "posses" read possess line 41, for "naphthalent read naphthalene lines 7 to 15, in the table column 4,

line 53', strike out "a"; column 'Z first column thereof last line, for "20 read 20% column 8, line 1 for "standing" read staining Signed and sealed this 2nd day of May 1961.

(SEAL) Attest:

ERNEST W, SWIDER DAVID. L, LADD Commissioner of Patents Attesting Offic'r 

1. THE METHOD OF MAKING A RESILIENT SMOOTH-SURFACED FLOOR COVERING COMPRISING FORMING A WATER-REPELLENT, BEATER SATURATED FELT CONTAINING BUTADIENE-STYRENE COPOLYMER DEPOSITED ON THE FIBERS AS A BINDER THEREFOR, DEPOSITING ON ONE SURFACE OF SAID SHEET A DECORATIVE WEAR-RESISTANT LAYER, SUBJECTING SAID LAYER TO ELEVATED TEMPERATURES, SUPPLYING TO THE OTHER SURFACE OF SAID FELT A MASS OF FOAMED LATEX CONTAINING A VULCANIZING AGENT, A GELLING AGENT, AND AT LEAST ABOUT 50% BY WEIGHT FILLER BASED ON THE WEIGHT OF RUBBER SOLIDS IN SAID LATEX, LEVELING OFF SAID MASS TO FORM A FOAMED LATEX LAYER OF EVEN THICKNESS IN THE RANGE OF 1/32" TO 1/4", GELLING SAID FOAMED LATEX LAYER, AND HEAT TREATING SAID FOAMED LATEX LAYER TO CAUSE DRYING AND VULCANIZATION THEREOF. 